1. Field of the Invention
The present invention relates to a novel device for taking a three-dimensional and temporal optical imprint in color of a volume of a few cubic centimeters at the surface of the human body, ensuring its structural integrity, applicable in the dental field for taking intraoral pictures, but also ensuring in this field, an assistance for diagnostic, including a miniaturized stereo system associated with one or several electronic CCD or CMOS color sensors for a specific and modulated lighting with LEDs of one or several wavelengths permitting to measure specular or Lambertian uniform surfaces without deposit of a “coating” on the surface of the teeth or gums, a central analog-digital data control and conversion unit, but also and eventually color and movement analysis software for assisting diagnostics by reflection, global or selective penetration of the light radiation of judiciously selected LEDs into the lighting used, without requiring the slightest mechanical, optical or electro-optical scanning.
2. Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 37 CFR 1.98.
The taking of imprints by optical means in order to perform diagnostics or make prostheses was described for the first time in 1973 by the applicant in his graduate thesis (DDS) under the title “Optical imprint”. The applicant has made numerous publications on this matter. He namely filed the first patent dealing with the interference for taking intraoral optical imprints in U.S. Pat. No. 4,663,720 and U.S. Pat. No. 4,742,464, and also in U.S. Pat. No. 4,611,288, but also in U.S. Pat. No. 5,092,022. The applicant also proposed the taking of optical imprints in dentistry and medicine through projecting masks, FR 84.05173), scanning in profilometric phase in conical projection, U.S. Pat. No. 4,952,149, or through dynamic monitoring by means of LEDs, WO 94/00074.
Since 1982 many papers deal with the taking of optical imprints through scanning in profilometric phase in parallel projection, the modeling or machining of the prosthesis.
All these works and inventions have led to many embodiments and more than twenty commercially available systems.
Since 2000, different solutions have been proposed, not in the mouth, but on plaster models made from imprints made in the mouth using traditional methods, for example in U.S. Pat. No. 7,399,181, or on models built by stereo-lithography, U.S. Pat. No. 10,726,257. This solution has also been proposed in addition to the systems for dentists with a scanning on a model by projection of dots or frames, U.S. Pat. No. 7,335,876.
In the field of orthodontics other proposals have been made to use the optical imprint, as shown in U.S. Pat. No. 7,361,018. These systems have i.e. permitted the commercial development of the system described in U.S. Pat. No. 7,361,017, U.S. Pat. No. 7,393,208, or U.S. Pat. No. 6,318,994, U.S. Pat. No. 6,802,713, U.S. Pat. No. 11,405,972.
As can be seen, among all these systems, few are transposable to the mouth for the following reasons:                the scanning is too slow, the scanning passes from 2 minutes per tooth to 2 seconds for the fastest ones,        the apparatus requires having a camera in constant position with respect to the object, which would require to fix the camera, and the patient's head, and        the displacement mechanism remains complex and inaccurate.        
In addition to these drawbacks, all the so-called laboratory systems, which scan a model, lead the dentist to perform a traditional imprint, which does not eliminate the discomfort for the patient and the inaccuracy of the intraoral molding and requires the practitioner to send the part to the laboratory. In addition to this drawback, the technician, when molding the imprint, will add further errors, which considerably affect the accuracy of the optical imprint on which he will work with his computer-assisted design software (CAM) after scanning.
Nowadays, the systems operating in the mouth are presently very few. All these systems use mechanical, optical or electro-optical scanning to perform the measurement of the surface under examination. These methods can be classified into three types, one using the profilometry of the phases in parallel projection in visible or blue light, with conical projection, by scanning of red or infrared fringes in about one hundred milliseconds, and finally, recently the system described in U.S. Pat. No. 7,372,642.
Nevertheless, all these intraoral cameras, the one developed by the present applicant included, have several particularly prohibitory drawbacks:                these systems are complex to be implemented and require much care in calibration;        the electronics remains complex, which makes it difficult to reduce the price and makes the camera fragile;        the cost of the camera is particularly high and can exceed 30,000; and        the cameras are generally bulky and heavy, which hinders the user.        
In fact, a closer analysis shows that these cameras have several very important drawbacks, in the very principle of the methods used. These drawbacks are unavoidable, because they are related to the choice of these methods.                a) All these systems, whether in the mouth, on the skin or in the laboratory (on a model), whether they use the OCT (Optical Coherence Tomography) in dermatology or ophthalmology, use the scanning of the surface by mechanical, optical or electro-optical means. Although this scanning of fringes or frames is very fast, it nevertheless requires a movement in the camera itself, which movement can cause blurs or parasitic displacements, which often lead to the rejection of part of the pictures.        b) this scanning significantly limits the field depth already significantly reduced in a macroscopic picture (of a few cubic centimeters).        c) the dots of the surface of the object are not measured, but instead the deformation of a light projection on the surface of this object is measured. This first feature requires the developers to cover the teeth with a white layer, referred to as “coating”, which degrades in principle the actual measurement of the object. This is indeed often expressed as both an inaccuracy and an inconvenience in the use of the cameras in the mouth.        d) this has obliged the manufacturers to use radiation making the tooth “opaque”, as with blue or ultraviolet rays. This is why the present applicant proposed a device using an argon laser. This can be restrictive for the user, even dangerous for the patient.        e) moreover, not measuring the object, but the distortion of the projected light, either a dot, a line, a frame or a phase of this light, eliminates all possibilities of having a perfect match between the color, the shade of the object and its measurement. The only shade that we can have is the color of the projected light.        f) passing from 3D reading to 2D reading in color, when it is used for diagnostics, is completely impossible in dentistry, because only a monochromatic image representing the light of the fringes is recovered.        g) finally, the analysis techniques by profilometry or scanning require to take several pictures of the same spot in order to be capable of extracting the third dimension. This results into a risk of distortion of the data between the first and the last picture, which leads to large errors in correlation and accuracy. The “movement” has always been the enemy of this type of technology.        
Finally, though it is possible to measure a tooth, the projected light is still measured, and not the object itself, and this measurement requires to use movements of the source or optics during the reading. As stated above, all these systems are based on the measurement of the distortion of the light displaced and viewed by the camera.
It should be noted that the same also applies in the field of dermatology or ophthalmology. The methods used in 3D reading are recent, expensive and complex, as the OCT apparatus show. That is why these disciplines mainly use 2D measurements, which are less burdensome for anatomical subcutaneous studies or their expansions to the (eventual) pathology.
The techniques used nowadays are the following:                a) videodermatoscope, which consists of a currently widely used basic tool, permitting to have an amplified image of the skin (up to 70×). The digital technology allows taking digital photographs as well as records, which thus facilitates the comparison over time and the sharing of information between clinicians. The devices offer on the other hand ancillary functionalities, such as the possibility of using light sources of different wavelengths for illuminating the skin, or also image processing such as the automatic segmentation of the lesions or also the automatic extraction of ABCD criteria.        
The cost of such a device remains however high, and no clinical study seeking to show an improvement in the diagnosis compared to the simple clinical examination has been found. Moreover, the videodermatoscope does not provide information in depth.                b) echography, which allows in-depth exploration of the lesions. With frequencies in the range from 10 to 50 MHz, it is possible to go down to 12 mm with an axial resolution of 150 microns. This technique is used for the study of the subcutaneous extension in pre-operative analysis and the search for metastatic melanoma, where it has shown excellent capabilities in terms of sensitivity and specificity. However, the proper use of such a device requires, however, to acquire some experience in reading ultrasound images; on the other hand, it is much more difficult to add informative post-processing on these images, unlike with the multispectral techniques (see below).        c) the OCT, which is based on interferometric optical techniques, allowing imaging the skin in depth in 3D with good lateral resolution (in the range of 15 μm), higher than that of the echographs. It allows, on the other hand, to carry out imaging almost in real time, but is limited in depth (maximum 1.5-2 mm). Only one device is currently marketed, and the study of its efficiency in the diagnosis of melanoma is currently under study. Though it has a very good resolution in real-time imaging, it operated on a small depth, has no clinical data, operated in cross-section, is difficult to implement and is very expensive.        d) confocal microscopy, which provides 3D images of the epidermis and papillary dermis with very high resolution (1-2 μm lateral resolution, 3-5 μm axial resolution). Its main drawback is that it is very limited in depth (200-500 μm).        
These devices have the advantage of having an excellent resolution, a very good melanoma/nevus discrimination (better than the clinical examination alone). But, apart from being of a very high cost, they have a very small depth of analysis.                e) multispectral imaging, which is the technique that has the highest interest today because of the simplicity of the method and its good price/quality ratio. It is indeed a simple imaging technique: it assumes that the skin is organized in layers, and that each layer includes different proportions of substances referred to as chromophores, which have each a relatively characteristic light-absorption spectrum. The main chromophores of the skin are melanin, collagen and hemoglobin, one understands the importance of this method in the study of melanoma, where the proportion of melanin will be changed over a more or less large number of layers. In order to obtain quantitative spatial information on these chromophores, different monochromatic lights (typically ten) are projected onto the skin, and the light re-emitted by the cutaneous skin is measured for each wavelength. One thus obtains information in depth, on which automatic processing can be applied, namely segmenting the lesions, obtaining the ABCD criteria in depth of same and quantifying their proportion of chromophores. However, only depths in the range of 2.5 mm can be reached. The main advantages of the devices are their technique, which is easy to be implemented, the many automatic processing operations that are possible and their good melanoma/nevus discrimination (better than the clinical examination alone). They have the disadvantages of operating only in 2D, of still being expensive, and of operating on a rather limited depth.        
There are of course methods under study for skin pathologies using the principles of IRM, PET—scan, of two-photon imaging or of terahertz imaging, but their implementation will be long and it will lead to devices too expensive to be used in private medical offices, which remains the goal to be reached.
Finally, there were some stereographic measurement tests in medicine using two or more than two sensors, which, through the triangular position method, permit to find the third dimension. The use of two sensors permits a stereo vision in well-defined objects, but the methods of mathematical correlations are complex and expensive because the objects used as references are difficult to be identified. The manual action is almost always necessary and the tests performed on teeth proved unusable in the aimed distances and field depths.
Likewise, the development of the images referred to as “triplet imaging system” (L configuration) using cameras placed in an equilateral triangular position position provided valuable information for determining the third dimension by simplifying the triangular position, but the results proved unusable in the dental conditions outlined above. Indeed, all the systems used require knowing the displacement of the camera or of the object between two (or n) acquisitions.
All these drawbacks have led to provide an inexpensive universal solution meeting the criticisms made above.